Enhanced Interpretation of Tissue Protease Activity by use of Photographic Color Film as a Substrate

Abstract

The enzymatic digestion of the 1st colored layer of gelatin in a photographic color-film processed unexposed produce a transparent colored site. Thus the use of a colorfilm for the histochemical localization of protease activity has proved to be an improvement over the gelatin-silver-film use. The 3 pigmented layers of the reversible Ferrania 3M color film, 135/36 daylight type, DIA 28 are yellow, magenta and red, and each is only 7[mu] thick. Before use, the film is dampened with 0.15 M phosphate buffer pH 7.6 until the gelatin swells and placed in an incubator where the atmosphere is saturated with water vapor. Tissues, fixed in 4% formaldehyde-saline at 4 C for 24-28 hr., are cut at 10-20 [mu] on a freezing microtome. Sections are mounted as soon as possible on color-film and incubated. No free fluid should be left over the sections. After incubation the film is allowed to dry naturally and then protected with a cover glass applied with Canada balsam. It was possible to ascertain proteolytic activity in the digestive apparatus of the pigeon embryo on the 14th day of incubation, at the same time as the zymogen granules became visible through the electron microscope.